The present invention relates generally to the variety of tools commonly known as "rotary marking tools", and more particularly to the type of such tool which includes a wheel having on the periphery thereof raised characters for marking a workpiece with impressions in the form of the raised characters.
The present invention is an improvement over such tools as disclosed in U.S. Pat. No. 2,996,977, issued on Aug. 22, 1961 to Jerome Friedman. In the aforementioned patent, the tool is disclosed as having a block upon which is rotatably connected a marking wheel having raised characters on the periphery thereof for marking a workpiece in the form of the raised characters. A pawl is pivotally connected likewise to the block adjacent to the marking wheel and terminates in a beak which remains in contact with the periphery of the marking wheel. The means for urging the beak of the pawl into engagement with the periphery of the wheel is a tension spring disposed along the outside of the wheel and having one end anchored to the pawl and an opposite end anchored to an outer or exposed extension of a stop-pin affixed to the marking wheel eccentrically of the axis of rotation of the wheel.
The stop-pin is engageable in one direction of the rotation of the marking wheel with an abutment provided on the block for defining at-rest position of the marking wheel. A notch is formed on the periphery of the marking wheel remote from the stop-pin and is adapted to received the beak of the pawl when the marking wheel is rotated a distance away from its at-rest position. When the beak of the pawl penetrates the notch in the marking wheel, it prevents the marking wheel from rotating further away from the at-rest position thereof.
A disadvantage associated with the tool disclosed in the aforementioned patent results from the need to often move the marking wheel axially thereof into close proximity with a collet or workpiece holder for purposes of marking the workpiece adjacent to the collet. However, the construction of the marking wheel is such that it cannot be moved into close proximity with the collet ("close proximity" meaning, for example, approximately 0.015 inches axially away from the collet). This is because a pulley projects axially outwardly from the end face of the marking wheel and interferes with the juxtaposition of the wheel close to the collet.
The pulley is affixed to and rotatable with the marking wheel, and has a circumferentially disposed groove. That groove is adapted to receive the tension spring which interconnects the pawl and marking wheel to one another (on the outside face of the wheel) and expands during the rotation of the marking wheel away from its at-rest position. Thus, interference is caused not merely by the existance of the pulley, but also by the disposition of the tension spring on the outside face of the marking wheel.
Another disadvantage associated with the tool disclosed in the aforementioned patent is that since the tension spring which interconnects the pawl and the marking wheel to one another is mounted along the outside face of the wheel it is continuously exposed not only during the period of use of the tool, but likewise during the period in which the tool is manually handled prior to or after its use. As a result, the spring may be damaged should it inadvertently snag upon adjacent apparatus when used or if dropped or otherwise mishandled by its user.